At the present time the method most commonly used to press wool is to insert a bale bag into a press, the bale bag having four flaps which hang down on respective sides of the press, inserting the wool into the bale bag, and as the bale becomes filled with wool, to lower a "monkey" into the press to press the wool downwardly. The monkey is lowered several times during the filling of the bale, and the pressed wool is pinned by means of pins which extend through the walls of the bale. The pressure frequently used is about 12 lbs. per square inch when applied to the wool, resulting in a density in the bale of about 18 lbs. per cubic foot.
The bales are subsequently pressed to a higher density in a factory, in presses called "dumping presses" to a density of between 25 and 30 lbs. per cubic foot. Certain recently introduced presses are capable of achieving a density of 37 lbs. per cubic foot, but these are very high pressure presses and very costly. It is known that wool which has been subject to high pressure has a slight increase in strength, although the reasons for this are not completely understood.
One of the objects of this invention is to provide an improved press which is capable of achieving a relatively high density, thereby enabling the required weight to be packed into a bale on the farm at a high enough pressure that further dumping is not required.
We have found that wool does not behave as a semi-fluid, but that if wool is firstly pressed at relatively low pressure into a bale, subsequent dumping is unlikely to increase density above that 35 lbs. per cubic foot, owing to the failure of the wool to evenly distribute the pressures applied. We have found also that under relatively high pressure, that is pressure above 30 lbs. per square inch, the lanolin content of the wool causes the fibres to move relatively freely, and that it becomes possible to achieve a relatively high density. However we have also found that the high density requires not merely the application of high pressure, but also the application of high pressure to a relatively narrow strip of wool, considerably narrower than the width of the bale.